Lumbar segmental `instability': clinical presentation and speci®c stabilizing exercise management
P. B. O'Sullivan School of Physiotherapy, Curtin University of Technology, Selby Street, Shenton Park, WA, Australia
SUMMARY. Lumbarsegmental instability is considered to represent a signi®cant sub-group within the chronic low back pain population. This condition has a unique clinical presentation that displays its symptoms and movement dysfunction within the neutral zone of the motion segment. The loosening of the motion segment secondary to injury and associated dysfunction of the local muscle system renders it biomechanicallyvulnerable in the neutral zone. The clinical diagnosis of this chronic low back pain condition is based on the report of pain and the observation of movement dysfunction within the neutral zone and the associated ®nding of excessive intervertebral motion at the symptomatic level. Four dierent clinical patterns are described based on the directional nature of the injury and the manifestation ofthe patient's symptoms and motor dysfunction. A speci®c stabilizing exercise intervention based on a motor learning model is proposed and evidence for the ecacy of the approach provided. # 2000 Harcourt Publishers Ltd
INTRODUCTION Back related injury is a growing problem in the western industrialized world placing an increasing burden on the health budget (Indahl et al. 1995). Estimates oflifetime incidence of low back pain range from 60 to 80% (Long et al. 1996) and although most low back pain episodes (80±90%) subside within 2 to 3 months, recurrence is common (Hides et al. 1996). Of major concern are the 5±10% of people who become disabled with a chronic back pain condition which accounts for up to 75±90% of the cost (Indahl et al. 1995). In spite of the large number of pathologicalconditions that can give rise to back pain, 85% of this population are classi®ed as having `non speci®c low back pain' (Dillingham 1995). More recently there has been increased focus on the identi®cation of dierent sub-groups within this population (Coste et al. 1992; Bogduk 1995). Lumbar segmental instability is considered to represent one of these sub-groups (Friberg 1987). Traditionally, theradiological diagnosis of spondyPeter B. O'Sullivan, Dip Physio, Post Grad Dip Manip Physio, PhD, Private practitioner, West Perth, Lecturer, School of Physiotherapy, Curtin University of Technology, Selby Street, Shenton Park, WA 6008, Australia. 2
lolisthesis, in subjects with chronic low back pain attributable to this ®nding, has been considered to be one of the most obvious manifestations oflumbar instability (Nachemson 1991; Pope et al. 1992), with reports of increased segmental motion occurring with this condition and spondylolysis (Friberg 1989; Mimura 1990; Montgomery & Fischgrund 1994; Wood et al. 1994). Lumbar segmental instability in the absence of defects of the bony architecture of the lumbar spine has also been cited as a signi®cant cause of chronic low back pain (Long etal. 1996). A number of studies have reported increased and abnormal intersegmental motion in subjects with chronic low back pain, often in the absence of other radiological ®ndings (Sihvonen & Partanen 1990; Gertzbein 1991; Lindgren et al. 1993). The limitation in the clinical diagnosis of lumbar segmental instability lies in the diculty to detect accurately abnormal or excessive intersegmentalmotion, as conventional radiological testing is often insensitive and unreliable (Dvorak et al. 1991; Pope et al. 1992). Because of this, the ®nding of increased and abnormal intersegmental motion of a single motion segment on radiological examination is considered to be signi®cant only if it con®rms the clinical ®nding of lumbar segmental instability at the corresponding symptomatic level...